1. Field of the Invention
The present invention relates generally to a catheter for use in the clinical arrest of a beating heart, and more specifically to catheter for the retrograde administration of a cardioplegic fluid to the vasculature of the heart.
2. Description of the Related Art
When performing cardiac surgery, it is frequently necessary to temporarily arrest the beating of the patient""s heart before the desired surgery can be performed. The procedure for stopping the patient""s heart during surgery is known as cardioplegia. One recognized technique of performing cardioplegia is to introduce a cardioplegic fluid, typically a solution containing agents such as potassium, magnesium, or procaine, into the coronary arteries or veins, which supply blood to the heart muscle. This typically occurs after disconnecting the heart from the body""s circulatory system, the heart""s functions having been assumed by a heart-lung machine. The cardioplegic fluid interferes with the heart muscle""s response to electrical signals which normally command it to beat, thereby stopping the heart.
A surgeon can introduce cardioplegic fluid to the coronary-vessel system in either the antegrade direction, which is in the natural direction of blood flow, or in the retrograde direction, which is opposite the natural direction of blood flow. In antegrade cardioplegia, the cardioplegic fluid is directed into the coronary arteries, usually by injecting the fluid into the aorta near the coronary ostia, which join the coronary artery system to the aorta. The fluid then flows into the ostia and the coronary arteries, and eventually to the heart muscle itself.
Retrograde cardioplegia is often performed by infusing a cardioplegic solution into the coronary sinus, which is a sort of collection point into which drains most of the coronary blood supply through the coronary vein system. This infusion is done by inserting a catheter into the coronary sinus and injecting the cardioplegic fluid through the catheter. The catheter typically has a balloon which inflates to seal the opening of the coronary sinus, and one or more openings on the catheter distal of the balloon. The cardioplegic fluid flows the length of the catheter, exits at the distal openings, and then flows into the coronary sinus. From there it flows into the coronary veins to achieve cardioplegia. The balloon prevents the fluid from flowing back out of the coronary sinus in the undesired antegrade direction.
Various types of catheter have been developed for use in retrograde cardioplegia, but all have suffered from one or more drawbacks. Often the catheter incorporates a distal tip which either blunt or cut at an angle. This type of tip may have edges that can damage the tissues of the veins or coronary sinus during insertion of the catheter. Prior art catheters generally feature a cannula which has a uniform width all the way to the distal tip, which can make it difficult for the surgeon to insert the distal end of such a catheter into the veins or sinus. Another problem frequently observed is a catheter with only transverse infusion openings, which are formed in the sidewalls of the cannula, or only an axial infusion opening, at the very tip of the cannula. This type of catheter is easily occluded at the distal end, either by a vessel structure which fits very closely around the cannula sidewalls, or by an obstruction in the vessel just distal of the catheter tip.
One aspect of the invention is an improved retrograde cardioplegia catheter.
Another aspect of the invention is a retrograde cardioplegia catheter which is easier to insert into the veins or coronary sinus.
Yet another aspect of the invention is a retrograde cardioplegia catheter which will not cause trauma to coronary tissues when being inserted.
Still another aspect of the invention is a retrograde cardioplegia catheter which may incorporate the above features with a self-inflating balloon and a pressure monitoring capability.
Accordingly, there is provided a catheter having an elongated cannula with an infusion lumen, and a portion of the cannula which tapers to form a distal end which is narrower than the more proximal portions of the cannula. The distal end of the cannula forms at least one infusion lumen opening. A balloon is attached to and surrounds the cannula near the distal end while being in fluid communication with the infusion lumen through one or more inflation openings. The infusion lumen openings are smaller than the inflation openings so as to make the balloon self-inflating.